You can copy the customized language folder e.g. English and rename it to something else. Eg English_custom
Then the English_custom language will be available in your Softaculous Panel and you can select that language and the files in this folder will not be overwritten.

I knew that but i use RVskin which automatically select the language of Softaculous so that do not work for me as i have to also edit the Spanish language and need both called by default English and Spanish, if this is the only way that Softaculous language can be overwrite you have to seriously work out something else guys. As many other product perhaps creating an "overwrite" directory into the language directory so any language file variables modified on it have precedence.

If you wish to modify Language you can send us the translated files we will publish the files in the next version. And for this we will also provide you a Softaculous Premium license until you maintain the translations.

I have to get this right, for me it is an very big problem, i have danisk language in all that Softaculous have translated, problem is that when an new version of ex. Wordpress get released it will overwrite the "older" Danisk version in the Softaculous panel, meaning that every time an new version is out my danish language is gone for that script.

Sir when there is an update in a script all the files will be replaced. If you wish to translate the package files you can add the script as a custom script so that the files are not overwritten and when there is an update the script you can make the changes in your custom script and restore your translation accordingly.

Which language did you translate ? You can email us the package and we will publish it. Also if you wish not to overwrite the files you can add this as a new language :
/path-to-softaculous/enduser/languages/
and these files will not be overwritten by Softaculous.